Preparation of composite powders based on titanium-chromium diboride by the method of plasma spheroidization for gas-thermal spraying and surfacing of protective coatings

To obtain the coatings with various special properties, such as heat- and wear resistance under friction conditions at high speeds, loads and the absence of lubrication, refractory compounds and composite materials based on them in the form of powders are used. The properties of composite powders, as well as coatings obtained from them, depend on the method of their production [1]. The goal of the work is to obtain composite metal-ceramic powders with good technological and mechanical properties for gas-thermal spraying and surfacing of coatings. Powder mixtures (Ti,Cr)B2 –NiAlCr, (Ti,Cr)B2 –AlN(SiC)–NiAlCr were obtained by mixing in a planetary mill. The particle size was ~3÷12 µm. Subsequently, the powder mixtures were conglomerated using organic binding materials, after which the particle size was ~40÷90 µm. These powders were passed through a plasma jet, causing them to sinter and become spherical. For powders, fluidity, bulk density, microhardness, microstructure, phase and chemical composition were studied. Detonation method coatings were sprayed from the powders. Spheroidized powders have good technological properties: fluidity τ=33÷74 sec., bulk density ɣ=1,76÷3,05 g/cm 3 . A single particle of powder has a spherical shape with high strength and microhardness Н µ =870÷3300 MPa which are comparable to the values of sintered compact materials. Powder particles have a heterophase microstructure with a uniform distribution of metallic and refractory components. (Ti,Cr)B2 –NiAlCr powders have the best technological and mechanical properties. Powders with AlN and SiC additives have a more branched particle surface. With increasing AlN and SiC content the surface of the particles becomes rougher and the fluidity of the powders worsens. Detonation coatings from the resulting powders have a heterophase microstructure with a uniform distribution of structural components. The adhesion strength of the coatings to the base is σ=91÷115 MPa and the density is 98÷99%.